JP5405966B2 - Intermediate transfer belt and image forming apparatus having the same - Google Patents

Description

  The present invention relates to an intermediate transfer belt used in an image forming apparatus for forming an image by an electrophotographic method such as a copying machine, a facsimile machine, a printer or the like.

  The electrophotographic image forming apparatus employs an intermediate transfer system in which the developer image carried on the surface of the developer image carrier is primarily transferred to the intermediate transfer belt and then secondarily transferred from the intermediate transfer belt to the recording medium. There is something to do.

  In such an image forming apparatus, a developer image produced on an endless (seamless) intermediate transfer belt spanned between a driving roller and a driven roller is transferred to a transfer roller that is in pressure contact with the driving roller across the intermediate transfer belt. When passing through, the developer image is secondarily transferred to the recording medium by applying a transfer voltage.

  When an endless intermediate transfer belt is used, there are problems such as assembly accuracy and component accuracy of the drive system roller, and a phenomenon such as meandering and skewing that moves in one direction of the roller shaft during rotation often occurs. . In order to prevent this, a system in which a skew feeding prevention member (called a beat) is provided on the back surface of the intermediate transfer belt is employed (see, for example, Patent Document 1).

JP 2008-304865 A

  Usually, the skew feeding prevention member (beat) is a strip-like sheet shape that is not seamless. When the material of this beat is only a rubber-based material such as urethane, there is a problem that the joint between beats is not stable due to expansion and contraction when pasting to the back of the seamless intermediate transfer belt body, and the beats are overlapped or too far apart have. Therefore, a laminated structure in which a urethane rubber member is combined with a base material of a polyethylene terephthalate (PET) sheet having a high elastic modulus and little expansion and contraction. If the entire beat is made of only a PET sheet, the rigidity is too high, and the intermediate transfer belt cannot smoothly rotate and cannot run stably.

  However, since the above beat is used by directly adhering polyurethane resin to the base material for beets mainly composed of PET sheet, when the travel amount of the intermediate transfer belt increases, the polyurethane resin is scraped off due to friction, etc. The scraps were scattered in the machine, causing a problem that affects image formation and the like.

  According to Patent Document 1, the guide members 4 are provided at both end portions 39 a of the driven roller 39. The guide member 4 is made of an elastic member such as urethane, and is designed to be less rigid than the meandering prevention guide 6, so that even if the meandering prevention guide is not arranged linearly, it is not affected by it. A belt conveying device and an image forming apparatus that can effectively prevent meandering of an endless belt have been disclosed, but there is no mention of scraping of the meandering prevention guide (beat) itself and the structure of the beat.

  Therefore, in the present invention, by adopting a skew prevention member using a resin instead of polyurethane resin, in an image forming apparatus using a seamless intermediate transfer belt, the intermediate transfer belt is prevented from meandering and skew. An object of the present invention is to provide an intermediate transfer belt that can transfer a good image onto a recording medium and that does not cause internal contamination due to beat wear even in long-term use.

  In order to solve the above problems, the present invention is an intermediate transfer belt used in an electrophotographic image forming apparatus, and is provided on an endless belt body carrying a toner image, and on the back surface of the belt body. A skew prevention member, wherein the skew prevention member includes a resin layer containing a polycarbonate-based polyurethane.

  According to the said structure, the resin layer containing a polycarbonate-type polyurethane is strong in strength compared with the resin layer which consists of normal polyurethane, and is excellent in abrasion resistance. As a result, in-machine dirt caused by the beat can be prevented without causing beat scraping. As a result, image defects such as transfer defects can be suppressed.

  The resin layer is composed of only polycarbonate-based polyurethane, and other resins can be blended like ordinary polyurethane as long as abrasion resistance can be maintained. In addition, when blending a plurality of resins, in order to maintain good wear resistance, it is preferable that the main component is polycarbonate polyurethane.

  Conventionally, polyethylene terephthalate (PET) has been used as the base material for the skew prevention member. However, it has been found that when a resin layer containing polycarbonate-based polyurethane is bonded to a base material made of PET, the adhesiveness between the two tends to become unstable, and the adhesive strength between the two layers may be insufficient.

  Therefore, as a result of various investigations on a substrate suitable for a resin layer containing a polycarbonate-based polyurethane, the closer the solubility parameter value of the material constituting the substrate and the solubility parameter value of the resin material constituting the resin layer are, the closer It has been found that the adhesion between the substrate and the resin layer is improved. Specifically, the skew prevention member has a laminated structure in which the resin layer is laminated on the base material, and the solubility parameter value of the material constituting the base material is the solubility parameter value of the polycarbonate-based polyurethane. Equivalent 9-10 are desirable.

  Thereby, it becomes possible to ensure good adhesion between the base material and the resin layer and to integrate them. That is, the resin layer can be directly melt-bonded to the substrate, and a skew prevention member that can be easily attached to the belt body can be obtained. Specific examples of the material constituting the substrate include polybutylene terephthalate (PBT).

  The base material made of PBT has a thickness of 0.02 mm to 0.5 mm. If the thickness of the base sheet is less than 0.02 mm, the strength of the skew prevention member itself may be insufficient. On the other hand, if the thickness of the base sheet exceeds 0.5 mm, the rigidity of the skew feeding preventing member becomes excessively large, so that the pasting operation on the back surface of the intermediate transfer belt may be difficult. Therefore, the thickness of the base sheet of the skew prevention member is preferably 0.02 mm to 0.5 mm.

  The belt body preferably has a laminated structure in which an elastic layer is disposed on a base, the base is made of polybutylene terephthalate, and the base and the base are melt bonded.

  According to the said structure, it becomes possible to adhere | attach with a heating apparatus etc. instead of the adhesion | attachment method using a double-sided tape etc., and can reduce a number of parts. It is also possible to construct the skew prevention member only from a resin layer containing a polycarbonate-based polyurethane, and to construct the substrate from polybutylene terephthalate, and in this case, it is possible to melt-bond the substrate and the substrate. Become.

  The image forming apparatus equipped with the above-described intermediate transfer belt does not generate beat scraping and can prevent in-machine contamination caused by it. As a result, image defects such as transfer defects can be suppressed. A good image can be transferred to a recording medium.

  As described above, in the present invention, since the resin layer containing polycarbonate-based polyurethane is used as the skew feeding preventing member of the intermediate transfer belt, beat scraping does not occur, and in-machine contamination caused by the same can be prevented.

1 is a front sectional view of an image forming apparatus according to an embodiment of the present invention. 1 is a partial cross-sectional view showing an embodiment of an intermediate transfer belt according to the present invention. Sectional view including intermediate transfer belt and drive roller The figure which shows the relationship between the thickness of the base material, skew stability and defects Partial sectional view showing another form of the intermediate transfer belt

  EMBODIMENT OF THE INVENTION Below, the form for implementing this invention is demonstrated based on drawing.

  As shown in FIG. 1, the image forming apparatus 10 includes an image reading unit 100, an image forming unit 200, a paper feeding unit 300, and a control unit 400.

  The image reading unit 100 is disposed above the image forming apparatus 10 and includes an automatic document feeder (ADF) 90 and an image reading unit 20. The image reading unit 20 includes a first document table 21, a second document table 22, a first mirror base 23, a second mirror base 24, a lens 25, and a solid-state imaging device (CCD: Charge Coupled Device) 26.

  In the ADF 90, a document transport path 93 is formed from the document stacking tray 91 to the document discharge tray 92 via the second document table 22. The ADF 90 conveys documents one by one to the document conveyance path 93. The ADF 90 is rotatable about the back side so that the top surface of the first document table 21 can be opened and closed. By rotating the ADF 90 so that the front side moves upward to expose the upper surface of the first document table 21, it is possible to place the document on the first document table 21 by manual operation without using the ADF 90.

  Both the first document table 21 and the second document table 22 are made of hard glass plates.

  The first mirror base 23 and the second mirror base 24 are movable in the horizontal direction below the first document table 21 and the second document table 22. The moving speed of the second mirror base 24 is set to ½ of the moving speed of the first mirror base 23. The first mirror base 23 is equipped with a light source and a first mirror. The second mirror base 24 is equipped with a second mirror and a third mirror.

  When reading the image of the document conveyed by the ADF 90, the first mirror base 23 is stopped below the second document table 22. The light from the light source is irradiated toward the image surface of the document passing over the second document table 22, and the reflected light on the image surface of the document is reflected toward the second mirror base 24 by the first mirror.

  When reading an image of a document placed on the first document table 21, the first mirror base 23 and the second mirror base 24 move horizontally below the first document table 21. The light from the light source is irradiated toward the image surface of the document placed on the first document table 21, and the reflected light on the image surface of the document is reflected toward the second mirror base 24 by the first mirror.

  Regardless of whether or not the ADF 90 is used, the reflected light on the image surface of the document is incident on the CCD 26 via the lens 25 by the second mirror and the third mirror with a constant optical path length.

  The CCD 26 outputs an electrical signal corresponding to the amount of reflected light on the image surface of the document. This electrical signal is input to the control unit 400 as image data. In this way, the image reading unit 20 reads an image of a document and acquires image data. The control unit 400 outputs image data to the image forming unit 200 as necessary.

  The image forming unit 200 is disposed below the image reading unit 100, and includes an exposure unit 3, four image forming units 31, 32, 33, 34, an intermediate transfer belt unit 6, a secondary transfer roller 66, a fixing device 7, A paper discharge tray 67 and paper transport paths 68 and 69 are provided.

  The intermediate transfer belt unit 6 includes an intermediate transfer belt 61, a driving roller 62, a driven roller 63, and a tension roller. The intermediate transfer belt 61 is stretched between a driving roller (supporting roller) 62 and a driven roller (supporting roller) 63 to form a loop-shaped moving path.

  The image forming unit 200 uses the image data corresponding to the four hues of black and cyan, magenta, and yellow, which are three subtractive primary colors obtained by color separation of the color image. , 32, 33, and 34, image forming processing is performed. The image forming units 31 to 34 are arranged in a line along the movement path of the intermediate transfer belt 61. The image forming units 32 to 34 are configured in substantially the same manner as the image forming unit 31.

  The black image forming unit 31 includes a photosensitive drum 1, a charging device 2, a developing device 4, a primary transfer roller 5, and a cleaning unit 64.

  The charging device 2 uniformly charges the surface of the photosensitive drum 1 to a predetermined potential.

  The exposure unit 3 includes a semiconductor laser, a polygon mirror, a first fθ lens, and a second fθ lens (not shown). Each of the laser beams modulated by image data of black, cyan, magenta, and yellow hues is image-formed. Irradiate each of the photosensitive drums 1 of the sections 31 to 34. On each peripheral surface of the four photosensitive drums 1, electrostatic latent images based on image data of each hue of black, cyan, magenta, and yellow are formed.

  The developing device 4 supplies the toner (developer) of each hue of the image forming units 31 to 34 to the peripheral surface of the photosensitive drum 1 on which the electrostatic latent image is formed, and converts the electrostatic latent image into the developer image. To visualize.

  The cleaning unit 64 collects toner remaining on the surface of the photosensitive drum 1 after development and image transfer.

  The outer peripheral surface of the intermediate transfer belt 61 faces the four photosensitive drums 1 in order. A primary transfer roller 5 is disposed at each position facing the respective photosensitive drums 1 with the intermediate transfer belt 61 interposed therebetween. Each of the positions where the intermediate transfer belt 61 and the photosensitive drum 1 face each other is a primary transfer position.

  A primary transfer roller 5 is provided with a primary transfer bias for charging the toner with a negative polarity and a reverse polarity (plus) in order to transfer the developer image carried on the peripheral surface of the photosensitive drum 1 onto the intermediate transfer belt 61. Is applied by constant voltage control. As a result, the developer images of the respective colors formed on the respective photosensitive drums 1 are sequentially transferred (primary transfer) to the outer peripheral surface of the intermediate transfer belt 61 and transferred onto the outer peripheral surface of the intermediate transfer belt 61. An image is formed.

  However, when image data of only a part of the hues of yellow, magenta, cyan, and black is input, only a part of the four photosensitive drums 1 corresponding to the hue of the input image data is static. An electrostatic latent image and a developer image are formed. For example, in the monochrome printing mode, the electrostatic latent image and the developer image are formed only on the photosensitive drum 1 of the image forming unit 31 corresponding to the black hue, and the intermediate transfer belt 61 has black on the outer peripheral surface. Only the developer image is transferred (primary transfer).

  At the time of full color image formation in which image formation processing is performed in all of the image forming units 31 to 34, the four primary transfer rollers 5 press the intermediate transfer belt 61 against all the photosensitive drums 1. On the other hand, during monochrome image formation in which image formation processing is performed only in the image forming unit 31, the primary transfer roller 5 presses the intermediate transfer belt 61 against the photosensitive drum 1 only in the image forming unit 31.

  Each primary transfer roller 5 is configured by covering the surface of a shaft made of a metal (for example, stainless steel) having a diameter of 8 to 10 mm with a conductive elastic material, and the intermediate transfer belt 61 is formed with the conductive elastic material. A high voltage is applied uniformly to. As the elastic material, EPDM (ethylene / propylene copolymer rubber), urethane foam or the like is used.

  The secondary transfer roller 66 is in pressure contact with the drive roller 62 with a predetermined nip pressure across the intermediate transfer belt 61. The secondary transfer roller 66 corresponds to the transfer roller of the present invention. The secondary transfer roller 6 is a conductive resin and is made of a hard material. The secondary transfer roller 66 is for transferring (secondary transfer) the developer image carried on the outer peripheral surface of the intermediate transfer belt 61 onto a sheet as an example of a recording medium.

  The developer image transferred to the outer peripheral surface of the intermediate transfer belt 61 at each of the primary transfer positions is a secondary transfer position that is a position where the intermediate transfer belt 61 and the secondary transfer roller 66 are opposed by the rotation of the intermediate transfer belt 61. It is conveyed to.

  Sheets are stored in the sheet feed tray 81 of the sheet feed unit 300. In the paper transport path 68, a plurality of transport rollers 12A and 12B are arranged. The paper transport path 68 is arranged in a substantially vertical direction in order to send the paper stored in the paper feed tray 81 to the paper discharge tray 67 via the secondary transfer position and the fixing device 7.

  A plurality of transport rollers 12 </ b> C and 12 </ b> D are arranged in the paper transport path 69. The sheet conveyance path 69 is arranged from the downstream side of the fixing device 7 to the upstream side of the secondary transfer position in the sheet conveyance direction. A sheet discharged to the sheet discharge tray 67 after passing through the fixing device 7 is conveyed to the sheet conveyance path 69 with the rear end up to that point in front. As a result, the sheet is retransmitted to the secondary transfer position with the front and back sides reversed.

  The paper feed unit 300 is disposed below the image forming unit 200 and includes a manual feed tray 82 in addition to the paper feed cassette 81. Paper is stored in each of the paper feed cassette 81 and the manual feed tray 82.

  The paper feed unit 300 feeds paper one by one from either the paper feed cassette 81 or the manual feed tray 82. The paper stored in the paper feed cassette 81 is fed by the pickup roller 11A and conveyed to the secondary transfer position via the paper conveyance path 68. The paper accommodated in the manual feed tray 82 is fed by the pickup roller 11B and conveyed to the secondary transfer position via the paper conveyance path 68.

  A registration roller 13 is disposed on the upstream side of the secondary transfer position in the sheet conveyance direction. The paper fed from the paper feed cassette 81 or the manual feed tray 82 is abutted against the registration roller 13 with the registration roller 13 stopped. The rotation axis of the registration roller 13 is arranged in a direction orthogonal to the paper transport direction. When the leading edge of the sheet is abutted against the resist roller 13 in a stopped state, the skew is corrected when the sheet is skewed.

  The registration roller 13 starts to rotate at the timing when the leading edge of the sheet is aligned with the leading edge of the developer image formed on the surface of the intermediate transfer belt 61, and supplies the sheet to the secondary transfer position.

  In this embodiment, a pre-secondary transfer charging device 14 and a counter roller 15 are disposed in the vicinity of the upstream side of the secondary transfer position in the moving direction of the intermediate transfer belt 61. The secondary pre-transfer charging device 14 is disposed on the outer peripheral surface side of the intermediate transfer belt 61, and the opposing roller 15 is disposed to face the secondary pre-transfer charging device 14 with the intermediate transfer belt 61 interposed therebetween. The pre-secondary charging device 14 applies a charge having the same polarity (minus) as the toner charging polarity (minus) to the developer image carried on the outer peripheral surface of the intermediate transfer belt 61.

  When the sheet fed from the sheet feeding unit 300 passes through the secondary transfer position, a high transfer voltage having the same polarity (minus) as the toner charging polarity (minus) is applied to the driving roller 62. As a result, the developer image is secondarily transferred (transferred) from the outer peripheral surface of the intermediate transfer belt 61 to the surface of the sheet.

  The developer remaining on the intermediate transfer belt 61 after the developer image is transferred to the sheet is collected by the intermediate transfer belt cleaning device 65. The sheet on which the developer image is transferred is guided to the fixing device 7 and is heated and pressed by passing between the heating roller 71 and the pressure roller 72. As a result, the developer image is firmly fixed on the surface of the paper. The sheet on which the developer image is fixed is discharged onto the discharge tray 67 with the surface on which the developer image is fixed facing down.

  FIG. 2 is a diagram showing a cross-sectional configuration of the intermediate transfer belt 61 according to the present invention. The intermediate transfer belt 61 is basically provided with an endless belt body 40 and a skew prevention member (beat) 71 attached to the back surface of the belt body 40. The belt main body 40 has a three-layer structure in which an elastic body layer 42 made of an elastic resin and a surface layer 43 are laminated in this order on the surface side of a base body 41.

  For the substrate 41, a resin such as polyimide (PAI), polyetheretherketone (PEEK), polyamideimide (PAI), polyethersulfine (PPS), or polycarbonate (PET) is used.

  The hardness of the belt body 40 is adjusted by the thickness of the elastic layer 42. The thickness of the elastic body layer 42 is adjusted so that the hardness of the belt main body 40 falls within the range of 40 degrees to 60 degrees in terms of durometer A hardness as defined in JIS K6253, and is usually made of urethane rubber having a thickness of 300 μm. Has been.

  Since urethane rubber has moderate elasticity, a nip pressure necessary for secondary transfer can be generated between the intermediate transfer belt 61 and the secondary transfer roller 66. Further, the urethane rubber has high adhesiveness with the polycarbonate resin used as the substrate 41, and can enhance the durability of the intermediate transfer belt 61 itself. Furthermore, since urethane rubber is inexpensive, cost reduction can be achieved.

  Further, since the surface layer 43 is made of a fluororesin, deterioration of the intermediate transfer belt 61 and reduction in thickness due to friction with the cleaning blade of the intermediate transfer belt 65 and the paper can be suppressed. The performance can always be stabilized. The thickness of this surface layer 43 is about 10 μm.

  The skew prevention member (beat) 71 includes a strip-like base material 72 made of PBT resin (manufactured by Asahi Glass Co., Ltd., Baroque film FR1), a resin layer 73 made of polycarbonate polyurethane, and an adhesive layer 74 made of double-sided tape ( Sumitomo 3M Limited, 442JS). The base material 72 preferably has a thickness of 0.02 mm to 0.5 mm for the reasons described above.

  The polycarbonate-based polyurethane constituting the resin layer 73 is a polyurethane obtained by copolymerizing a polyol and a polyisocyanate, and the polyol has a polycarbonate-based polyol as a main component. Examples of the polycarbonate polyol include polyhexanediol carbonate, polynonanediol carbonate, and the like. The amount of each raw material is 30 to 180 parts by weight of polyisocyanate with respect to 100 parts by weight of polyol.

  Specific examples of such a polycarbonate-based polyurethane include Milactolan XN-2001, XN-2002, XN-2004 and the like manufactured by Nippon Polyurethane Industry Co., Ltd.

  The thickness of the resin layer 73 is 0.3 mm, and the resin layer 73 is directly melt bonded to the base material 72 made of PBT resin by heating. Adhesiveness between the base material 72 of the obtained skew feeding preventing member 71 and the resin layer 73 was good, and problems such as delamination did not occur even when it was attached to the intermediate transfer belt 61 and used.

  On the other hand, when PET is used as the resin constituting the base material 72, the adhesiveness between the base material 72 and the resin layer 73 becomes unstable, and an appropriate adhesive is interposed between the two layers. Action was required.

  This is because the solubility parameter of the PBT resin is 9 to 10, which is equivalent to the solubility parameter of the polycarbonate-based polyurethane, and the solubility parameter of the conventional PET resin is 10 to 11, and the polyurethane resin Since the solubility parameter is 10 to 11, the compatibility of both layers, that is, the solubility parameter of the material constituting both layers is considered to have a great influence on the possibility of fusion bonding.

  In the present embodiment, the double-sided tape 74 is attached between the base 41 of the intermediate transfer belt and the base 72 of the skew prevention member. However, the base / base that can be melt bonded by applying heat. In such a combination (for example, PBT / PBT), it is not necessary to use a double-sided tape.

  FIG. 3 is a sectional view including the intermediate transfer belt 61 of the driving roller 62 (see FIG. 1). The skew feeding prevention member (beat) 71 is formed in a belt shape and is attached so as to cover the entire circumference of both end portions in the belt width direction on the back surface of the intermediate transfer belt 61. Both ends (62a, 62b) of the driving roller 62 are arranged with a slight spacing from the skew feeding preventing member (beat) 71. Therefore, the drive roller 62 is not displaced in the axial direction during the travel of the intermediate transfer belt 61.

  FIG. 4 shows the thickness (mm) of the base material 72, the pasting workability to the intermediate transfer belt, and the image forming apparatus 10 when a plurality of types of intermediate transfer belts having different thicknesses of the base material 72 are prepared. It shows the relationship with running stability when it is installed. The rotational torque (N · m) for driving when the intermediate transfer belt 61 was actually mounted was also measured.

  The following was found from the experimental results. The smaller the thickness of the base material 72, the smaller the contact pressure between the skew prevention member 71 and the driving roller 62, and the smaller the rotational torque. Therefore, a small capacity drive motor can be used as a drive source. However, if the thickness of the base material 72 is less than 0.02 mm, the seam may not match during the pasting operation.

  On the other hand, when the thickness of the base material 72 exceeds 0.6 mm, the rigidity of the intermediate transfer belt 61 as a whole becomes too large, and thus it was confirmed that the rotational torque increases and the smooth rotation of the intermediate transfer belt 61 is impaired. .

  From the above, if the thickness of the base material 72 is 0.02 mm or more and 0.5 mm or less, the intermediate transfer belt 61 can be prevented from skewing and meandering, and the rotation performance is not affected. It can always be kept stable.

  FIG. 5 is a partially enlarged cross-sectional view showing another embodiment of the intermediate transfer belt 61, and the base 41 of the intermediate transfer belt 61 is made of PBT resin. The skew prevention member 71 is composed only of a resin layer 73 made of polycarbonate polyurethane, and this is directly melt bonded to the base 41 of the intermediate transfer belt 61. Thereby, it becomes possible to reduce the manufacturing process of parts such as double-sided tape and the skew feeding preventing member. The present invention can also be applied to an electrophotographic image forming apparatus capable of forming only a monochrome image.

  The above description of the embodiment is to be considered in all respects as illustrative and not restrictive. The scope of the present invention is shown not by the above embodiments but by the claims. Furthermore, the scope of the present invention is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

DESCRIPTION OF SYMBOLS 1 Heat exchanger 10 Image forming apparatus 20 Image reading part 31, 32, 34, 34 Image forming part 41 Base body 42 Elastic body layer 43 Surface layer 61 Intermediate transfer belt 62 Driving roller (supporting roller)
63 Follower roller (support roller)
66 Secondary transfer roller (transfer roller)
71 Skew prevention member 72 Base material 73 Resin layer 74 Adhesive layer 99 Paper (recording medium)
DESCRIPTION OF SYMBOLS 100 Image reading unit 200 Image forming unit 300 Paper feed unit 400 Control part

Claims (2)

An intermediate transfer belt used in an electrophotographic image forming apparatus, comprising: an endless belt body that carries a toner image; and a skew feeding prevention member provided on a back surface of the belt body, the skew feeding prevention The member has a laminated structure in which a resin layer is laminated on a base material, the base material is made of polybutylene terephthalate, the resin layer contains polycarbonate-based polyurethane, and the belt body is elastic to the base material. An intermediate transfer belt having a laminated structure in which body layers are laminated, wherein the substrate is made of polybutylene terephthalate, and the substrate and the substrate are melt bonded. Image forming apparatus characterized by mounting the intermediate transfer belt according to claim 1.

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